Otto e



0. E. RUHOFF.

DRY CELL MATERIAL AND METHOD OF MANUFACTURE.

APPLICATION FILED JAN.31, 1920.

Patented Sept. 20-, 1921.

OTTO E. RUHOIEF, OF MADISON, WISCONSIN, ASSIGNOR TO FRENCH BATTERY a CARBON 00., OF MADISON, WISCONSIN, A CORPORATION OF WISCONSIN.

i DRY-CELL MATERIAL AND METHOD OF MANUFACTURE.

Specification of Letters Patent.

Patented Sept. 20, 1921.

Continuation of application Serial No. 166,246, filed May 3,1917. This application filed January 31, 1920. Serial No. 355,479.

T 0 all whom it may} concern:

Be it known that I, OTTO E. RUHorF, a citizen of the United States, residing at Madison, in the county of Dane and State of lVisconsin, have invented a new and useful Improvement in Dry-Cell Materials and Methods of Manufacture, of which the folally consisting of manganese dioxid and pulverized coke or graphite, the carb0na-- ceous material being used as the electrically conductive ingredient for such a depolarizing mixture. The primary objectof the present invention is to provide an improved mixture of this character, employing therein an improved conductive ingredient, to greatly improve the strength, efiiciency, and life of the battery.

According to the present invention, I produce calcined lamp-black by subjecting ordinary or commercial lamp-black to a high temperature for a prolonged period, until the volatile constituents are substantially eliminated; and I employ the calcined lampblack product as a substitute for a part or all of the ordinary carbonaceous material, such as graphite, coke, or the like. ordinarily employed in battery mixtures for depolarizing purposes.

The accompanying drawing illustrates forms of retorts or furnaces adapted to the practice of the improved process. In the drawing- Figure 1 represents a longitudinal vertical sectional view of an electric retort. or turnace, adapted to the practice of the process: and Fig. 2 represents a traiisverse vertical sectional View of a gasheated retort which mav be employed.

Ordinary lamp-black, that is, lampblack as it is ordinarily nianuiactured and sold commercially, cannot be satisfactorily employed as such combictive ingredient. One method of producing such lamp-black is by burning jets of gas below a revolving plate and collecting the lamp-black which forms as a deposit on the plate. Lamp-black is thus produced by burning either natural gas or oil with a deficiency of air, or under such condition as to produce a deposit of the lamp-black upon the lower surface of the plate.

It is stated by one authority (see Vol. I, part 3, p. 480, Gmelin-Kraut, H a-mibuch dail-lnorganischen Uhemz'e of J9.Z])-that lampblack contains the following constituents:

92 to 93% C.

1 to 2% H.

Different makes of lamp-black may very considerably in composition, but the ordinary commercial varietics are not suitable for use in a depolarizing mixture, probably largely on account of the volatile substances contained in the lamp-black. It is probable, also, that the physical condition enters into the problem. That is to say, the calcined product. is probably harder and is more resistant to attack by chemicals, thus contributing to the increased shelf-lite of the battery. Good grades of commercial lampblack may contain as low as about one per cent. of volatile substances. but nevertheless are not well suited for use in a depolarizing mixture.

In preparing calcined lamp-black for use in a battery, in accordance with this invention, a quantity of ordinary or commercial lamp-black is placed in a suitable receptacle and subjected to a high temperature, red heat or above, for a suitable period of time. or until the volatile constituents are largely eliminated. The calcined product then allowed to cool, and may be then used at once in the manufacture of batteries: or. if desired, the material may be IilLFllVQil for any reasonable length of time and used, as required, in the manutacture of batteries.

The temperature indicated above may range from about 1000 upwardly. a very suitable temperature being about 1200* The heat is continued as long as may be necessary to eliminate the bulk of the who tile matter. the length of time varying with the grade of lamp-black employed and the degree of heat employed. 'l b-e time may vary from thirty minutes to several lion but it is desirable to continue the heat ti calcined, using this expression in the sense of eliminating by heat a high percentage of the volatile substances contained in com mercia-llamp-black. By reducing the volatile substancesto a trace, it has been determined that the calcined lamp-black affords an excellent material for use in a depolarizing mixture for dry cells. whereas the ordinary lamp-black is not at all suitable for such purpose. It was found, for instance, that with a certain grade of lamp-black, the continuous service of a battery employing a mixture containing such lamp-black as the conductive material gave an exceedingly short period of continuous lighting service, whereas the period of lighting service obtained by calcining the same grade of lampblack for a period of thirty minutes at a temperature of 1200 C. increased the period of lighting service nearly twenty fold. So, also, it has been found that various grades of ordinary lamp-black which were not at all suitable for use in battery mixtures were, by the calcining treatment. converted into a calcined product excellently suited to such purpose.

The calcining treatment may be effected by placing the lamp-black in a suitable receptacle, such as a mu fle, or a chamber, provided with heat-resisting .walls, and subjecting the materials to a high degree of heat in any suitable manner.

Lamp-black, being in the nature of a carbon deposit, is composed of exceedingly fine particles. Thus, measurements made by the micrometer of an oil immersion microscope reading to .00001 inch indicate, in a given grade examined, sizes ranging from 0.00002 inch for the finest particles to 0.00003 inch for the largest particles. The calcining temperature noted above is, of course, far below the temperature at which carbon graphitizes; and it may be remarked that proportions by weight afford a satisfactory battery mixture.

Calcined lamp-black 100 Manganese dioxid ore 594 Sal ammoniac 79 Water 80 Tests of batteries made in approximately the proportions set forth above, using in one case uncalcined lamp-black of a certain graphite alone, 1 hour 45 chemically pure graphite was used, while .1

the lamp-black used did contain impurities up to 5% ash, thus showing that the results obtained were due to the heating or calcining of the lamp-black and not to superior purity of the lamp-black as compared with the graphite. Ordinary pulverulent graphite is relatively exceedingly coarse in comparison with lamp-black, andsuch pulverized graphite is a material which is Very com monly employed in a depolarizing mixture.

As indicated above, the calcined lampblack may be substituted for a part of the graphite used in the depolarizing mixture of a battery. In such case, a good mixture, taking the materials by weight, is as follows:

120 pounds manganese dioxid ore.

16 pounds lamp-black (possible 20,000 mesh).

4 pounds of graphite (200 mesh).

16 pounds of sal ammoniac.

16 pounds of water.

In the table which immediately precedes, the proportion of calcined lamp-black with respect to the total carbonaceous material may vary. Good results can be obtained,

for example, by using about four pounds 10 g of calcined lamp-black to sixteen pounds of graphite. The lighter and flufiier the lampblack, the smaller may be its proportion in the carbonaceous material; and an increase in the proportion of the coarser mesh car- 1 bonaceous material results in increased conductivity, assuming that there is present a sufficient proportion of lamp-black to substantially fill the interstices and establish complete contact.

The battery mixture is introduced into the battery or dry cell in accordance with any suitable method of manufacture.

At the present day it is possible to obtain upon the market lamp-black containing a much lower percentage of volatile substances than is given by the authority referred to above, but none of the'commer'cial lampblacks known to me is suited to use as the conductive ingredient of a depolarizer. In-

deed, commercial lamp-black containing as low as one per cent. of volatile substances is not at all suited to use in a depolarizer. On the other hand, by a calcining operation, the volatile substances in the better grades of lamp-black may be reduced to less than onetenth of one per cent, and the calcined product may be employed in a battery mixture with results incomparably better than it is possible to obtain from the uncalcined lampblack. As has been indicated, the calcined product is more resistant to the action of chemicals than ordinary lamp-black. Thus, for example, tests in a mixture of nitric acid and potassium chlorate have shown a decrease of 25%, or more, in rate of solubility.

The use of calcined lamp-black results in bringing the conductive ingredient of the battery mixture into more intimate contact with the depolarizing-compound, and thus improves the operation of the battery. So far as this feature is concerned, the conduc'tive material may consist wholly of calcined lamp-black. on the other hand, the same object, is substantially gained and better internal conductivity is also attained by using as conductive material a suitable proportion of powdered graphite mixed with the calcined lamp-black, which, as has been indicated, possesses a degree of fineness of an entirely different order of magnitude from that possessed by the powdered graph-- ite.

Referring to Fig. l of the drawing, A represents a furnace composed of refractory material, which is provided with a longi tudinal chamber, or passage, A; and B, the terminals, or electrodes, of an electric circuit, in the form of iron plates which extend into the end-portions of the chamber A. In the employment of this furnace, the chamber, or passage, A, is packed with lamp-black C, and the openings at the end of the chamber are closed by plates, or blocks, D. Electric current is then passed through the charge in sufficient volume to heat the material to a temperature of approximately 1200 C. or 1300 C., it being understood that the lamp-black acts as resistance material in the circuit and thus becomes heated. This degree of heat may be advantageously continued until the volatile constituents of the charge are practically eliminated, or reduced to a trace. The period of heating may advantageously extend over a period of several hours. The length of time required to produce the best results will vary, depending upon the degree of heat, and the operation will be adjusted according to-convenience. For instance, a charge may be heated over night, or during a period of from eight to twelve hours; and, if desired, the degree of heat may be cut down during a portion of this time. The furnace is shown provided with under which the heating is carried ori are such as to prevent the passage of air through the charge, so that thr' charge will not burn or be consumed. If d shed, the ends of the chamber A may be closed by laying bricks therein, and plastering with asbestos cement to render the ends air-tight. Usually it will be found that at each end of the furnace is about one-sixth of the charge not properly calcined. buch portions may be rejected and mixed 'witha fresh charge.

In Fig. 2, E represents a furnace, or retort, and F represents a gas burner. The charge may be introduced into the passage E and the ends of the passage closed, after which heat may be applied; or, if desired, individual retorts, or vessels, containing the lamp-black, may be introduced into the chamber E'before the heating operation is performed. If desired, burning gases may pass throughthe. chamber E, assuming a retort or retorts to have been introduced. In any case, suitable provision for heat insulation is made.

The method illustrated in Fig. 1 has been employed on a commercial scale for a considerable period of time, and has proven thoroughly practicable and highly satisfactory.

In the appended claims, the expression; calcined lamp-black is to be understood as meaning ordinary or commercial lampblack which has been subjected toheattreatment of the character'set forth above.

The present application is in the nature of a continuation of my-application No. 166,246, filed May 3, 1917.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitation should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

WVhat I regard as new, and desire to secure by Letters Patent, is:

1. A depolarizing mixture for dry cells having as. one of its constituents calcined lamp-black obtained by subjecting ordinary commercial lamp-black to prolonged heat treatment at high temperature, .said calcined lamp-black being characterized by a relatively low volatile substance content.

2. A depolarizing mixture for dry cells comprising calcined lamp-black, said calcined lamp-black being substantially free from volatile substances; and a relatively coarse carbonaceous material mixed with said calcined lamp-black.

3. A depolarizing mixture for dry cells comprising calcined lamp-black, said calcined lamp-black being substantially free from volatile substances; and a relatively coarse pulverulent graphite mixed, in minor proportions, with said calcined lamp-black.

4. As a conductive constituent for use in a depolarizing mixture, calcined lamp-black containing less than one-tenth per cent. of volatile substances.

As a constituent of an electric battery depolarizing material, lampblack which, when compounded with other battery materials in approximately the proportions of 100 parts depolarizing material, 594 parts manganese compound or ore containing most of the manganese as dioxid, 79 parts sal ammoniac and 80 parts water, and used in a battery of an inch in diameter and 1% inches high in connection with the kind of lamp-bulb ordinarily used with a battery of such Size, such battery will give a lighting service in excess of 100 minutes.

6. The method of preparing a constituent for use in a depolarizing mixture, which comprises subjecting ordinary lamp-black to heat treatment at high temperature for a prolonged period until the volatile constituents of the lamp-black are largely eliminated.

T. The method of preparing an ingredient for a depolarizing mixture for dry cells, which comprises subjecting ordinary lampblaclr to heat treatment in a mufile for a prolonged period at high temperature until there is produced a calcined product having a low percentage of volatile constituents.

8. The method of preparing an ingredient for a filling mixture for dry cells, Which comprises subjecting ordinary lamp-black to heat treatment in a muffle for a prolonged period at high temperature until there is produced a calcined product having less than one-tenth percent. of volatile substance therein.

9. The method of preparing a depolarizing mixture for an electric battery consisting in subjecting ordinary lamp-black'to heat treatment in a suitable chamber at a temperature in excess of 1000 C. for a period of time in excess of thirty minutes; allowing the calcined product thus obtained to cool; then mixing 100 parts of carbonaceous material comprising such calcined product with other ingredients approximately as follows: 594 parts manganese compound or ore containing most of the manganese as dioxid, 79 parts sal ammoniac and 80 parts water.

10. The method of preparing an ingredient for a depolarizing mixture which comprises subjecting commercial lamp-black to heat treatment in a muffle, from which the air is excluded for a prolonged period at high temperature, such treatment being continued until the volatile constituents'are substantially eliminated.

11. The method of preparinga constituent for a depolarizing mixture which comprises introducing lamp-black into an electric circuit as resistance material and passing electric current therethrough under conditions which heat the lamp'black to a high temperature, the high temperature being maintained for a prolonged period.

12. As a conductive constituent for use in a depolarizing mixture, calcined lamp-black substantially free from volatile substances, and relatively coarse carbonaceous material mixed therewith, said calcined lamp-black constituting approximately 20% of the total carbonaceous material.

OTTO E. RUHOFF. 

